


Experimenting

by orphan_account



Category: haikyuu
Genre: Bottom growth, FTM, Incest, M/M, Osamu is actually a good brother, PIV Sex, Sibling Incest, Trans Character, Trans Miya Atsumu, Twincest, he's v supportive of Atsumu transitioning, miyacest
Language: English
Status: Completed
Published: 2020-09-25
Updated: 2020-09-25
Packaged: 2021-03-07 16:48:52
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings, Underage
Chapters: 1
Words: 1,429
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/26650945
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: The Miya twins are both virgins and decide they don't want that to be the case anymore.
Relationships: Miya Atsumu/Miya Osamu
Comments: 6
Kudos: 218





	Experimenting

**Author's Note:**

> I haven't proof read this so I'm sorry in advance for any mistakes!

"This is so fucked up." 

"No shit."

"But this is just experimentin'. We can forget all about it afterwards." Atsumu breathed, uncharacteristically anxious. Osamu wasn't much better though, both of their hearts racing as they sat on Osamu's bunk, the lower one, across from each other.

"Yeah. Right." Osamu swallowed down his anxiety. "C'mon, let's just... get naked already."

"Mm."

The two stood and turned away from each other as they undressed. Neither were shy about undressing usually, in fact there were multiple times in the past where either of them would just walk into their shared room naked after a shower while towel drying their hair... but this was different.

Atsumu was the one who proposed experimenting with each other - despite what everyone believed, they were both virgins, had barely even kissed anyone. Their teammates were the only ones who knew they'd both never had sex and Suna would often tease them about it... so Osamu couldn't really help but agree with Atsumu.

It was wrong, so fucking wrong. It was like fucking yourself - the only thing being that copy of yourself had different genitals than you did.

That was honestly the reason Atsumu hadn't lost his virginity yet. Only people close to him knew he was trans and had started his transition when he got to high school. Osamu just never really found anyone appealing enough to want to fuck, everyone was so fucking annoying. He definitely found Atsumu equally, if not more, annoying as everyone else, but it was just different somehow - especially with the promise of never having to speak of it again.

Their parents were out of town for a few days after all, so it was as good of time as any to make the gods cry.

They turned back towards each other after fully undressing, and despite Atsumu never being shy in the locker room, he had his arms crossed over his chest now, hiding one of two things they weren't identical in.

That actually made Osamu roll his eyes. "Drop yer fuckin' arms, I've seen yer chest plenty of times already." He sighed, stepping forward when Atsumu didn't immediately listen, grabbing the older's arms and manually uncrossing them - surprisingly getting no resistance.

"Yeah, but never like this."

"Obviously." Osamu scoffed before his features softened. "You can wear a shirt if it makes ya more comfortable."

Atsumu was the one to sigh this time, shaking his head. "As if you seeing me naked would make me uncomfortable." He muttered, taking a seat on the bed.

Osamu took a seat beside him after retrieving the lube and condoms he'd stashed away after Atsumu had proposed them losing their virginities to each other just a couple hours earlier. "Lie down."

Atsumu did as told without any complaint but kept his thighs together as Osamu kneeled at his feet with a raised eyebrow.

"How the hell am I supposed to put my dick inside ya if ya won't open yer legs?" He put his hands on Atsumu's thighs and eased them open until he was settled with the older's legs draped over his, a few inches between their genitals.

Atsumu watched with a racing heart as Osamu opened the lube and poured some onto his fingers, rubbing the gel between them before prodding them against the older's entrance. He probably didn't need the extra lubricant, or preparation, but Osamu definitely didn't want to end up hurting his brother in this kind of situation. There's not really anything he could give as an explanation that would be believable as to why Atsumu was in pain in such an intimate area other than "we fucked."

Osamu worked his fingers inside Atsumu, adjusting the angle of them when he'd receive a hitched breath from the setter, and before he knew it, he was rock hard, getting off to the surprisingly shy noises that left the older. After three seemed to fit comfortably, Osamu figured that was more than enough preparation and slipped his fingers out to roll on a condom - the last thing they needed was evidence of what they'd done in the form of morning sickness and knowing glances as Atsumu's stomach swelled.

He smeared the leftover lube from his fingers onto the condom as he inches forward a bit so their hips were flush, just experimentally grinding up against the wet heat that felt incredible already even through the rubber. After what felt like hours of just grinding together, and forcing a shudder out of Atsumu every time Osamu would firmly rub against his growth, the younger finally aligned himself with the slicked up entrance, slowly easing in inch by inch.

Osamu was definitely above average in terms of both length and girth. He wasn't hung like a horse or anything like that, but he was big enough to knock the wind out of someone - and that someone happened to be his older brother who was gripping the sheets, his head tilted back and mouth agape with closed eyes and knitted brows as he struggled to relax under the both painful and satisfying stretch, unconsciously clenching and unclenching around Osamu's dick as he drew in shaky breaths.

The dick's owner in question noticed how much the other was struggling, and he himself was struggling not to cum immediately from the overwhelming sensation, and decided in an almost intoxicated haze to distract him. The distraction he chose was to press open mouth kisses along Atsumu's bared throat, dragging his tongue along the heated flesh before playfully nipping it - none of his actions were deliberate enough to leave a mark but it had Atsumu's pulse quickening and his adam's apple bobbing as he swallowed hard.

"M-Move." Atsumu's demand was interrupted with a voice crack that Osamu would've normally teased him for, but it wasn't the time for that. They both fell into a silence filled only a wet squelch every time their hips met and their nearly labored breaths, similar to how they'd sound after a particularly long volleyball game except neither of them were wanting to cool down yet. All either of them could focus on were the hands against Osamu's biceps, the fingers gripping Atsumu's hips with a bruising force, and the pleasure they both experienced after every movement, no matter how uneven and obviously inexperienced.

Their breathing was the least of their concerns.

"A-Ah! 'Samu! Shit, right there-" Atsumu's cries broke them both out of their trances and Osamu couldn't help the satisfaction he got as he started angling his thrusts all towards that spot, resulting in a nearly sobbing Atsumu with tears streaking down his cheeks and nails leaving blunt red lines in their track from Osamu's biceps to now his shoulder blades as he clung to him desperately. "Yes! F-Fuck, 'Samu... 'Samu.."

"Yer so damn loud." Osamu grunted, his mouth returning back to its previous fascination as he nosed behind Atsumu's ear, teasing the flesh and getting a gravelly moan as an immediate response to teeth grazing against it. Taking that as initiative, Osamu trapped the skin between his teeth as he sucked harshly, leaving a dark red blemish in his place and a trembling Atsumu.

It didn't take long after that for Atsumu to move a hand between them and desperately rub his growth, starting to rock his hips against Osamu's merciless thrusts until he was crying out. "'Samu! Fuck, 'm gonna-" He was cut off by his own moan as he clenched down tightly around Osamu's dick, body trembling and fingers quickly working.

Osamu wasn't far behind, the sudden tightness too much as his hips shuttered and he spilled into the condom.

They just stayed like that for a few moments, Osamu's face hidden in Atsumu's neck, them both still connected and trembling from the aftershock of their orgasms. It wasn't until after their highs had dissipated that Osamu carefully pulled out and tied off the condom, finally settling down beside his twin on the bunk.

"Holy shit." Atsumu breathed out with a little airy laugh. "That felt really fuckin' good."

Osamu let out a breath. "Yeah."

Silence settled between them comfortably, both drowsy and thoroughly exhausted. Hesitantly, Atsumu hooked his pinky with his brother's between them on the bed.

"I... don't wanna forget about that."

Osamu didn't say anything for almost a minute and Atsumu actually thought he wasn't going to until he felt the younger's pinky tighten around his.

"Me neither."

"What does this mean for us?"

"I don't know." Osamu confessed, finally turning his head to look at the other. "I guess we'll just... figure it out later."


End file.
